Field of the Invention
The invention relates to a process for the production of a honeycomb body in which sheet metal layers that are at least partially structured for forming passages through which a fluid is able to flow, are stacked and/or wound in layer-wise manner.
A honeycomb body of the above-indicated kind is known, for example, from International Publication WO 89/07488, corresponding to U.S. Pat. No. 5,102,743. The honeycomb body serves as a carrier for a catalyst which promotes the conversion of components of an exhaust gas, in particular an exhaust gas from an internal combustion engine, into compounds which are less environmentally polluting. The honeycomb bodies are exposed to high levels of mechanical and thermal loading. Besides the mechanical and thermal loadings, the sheet metal layers are exposed to an atmosphere which promotes corrosion. It is therefore desirable to use sheet metal layers which have a high degree of resistance to corrosion for producing a honeycomb body.
U.S. Pat. No. 5,366,139 discloses using sheet metal layers for honeycomb bodies which firstly are formed of a layered or laminate material. Such sheet metal layers have at least one layer of chromium-containing steel and at least one substantially aluminum-containing layer. A sheet metal layer of that kind is subjected to a heat treatment, with the sheet metal layer being substantially homogenized. The expression "homogenization of the sheet metal layer" is used to denote diffusion of the aluminum into the steel so that the result is essentially a single-layer sheet of steel with aluminum.
U.S. Pat. No. 5,366,139 discloses firstly implementing the heat treatment under vacuum or in a reducing and finally an oxidizing atmosphere. The treatment of the sheet metal layer in the oxidizing atmosphere causes the formation on the sheet metal layer of an oxide skin or a film which serves in particular as a bonding layer for a washcoat that is to be subsequently applied. The production of such sheet metal layers is relatively cost-intensive since the sheet metal layers have to be subjected to a heat treatment for homogenization purposes.